Acetate fibers are one of the principal types of synthetic fibers. The fiber forming substance is cellulose acetate in which at least 92% of the hydroxyl groups are acetylated. This fiber is called triacetate or triacetate cellulose. Secondary acetate contains only about 76 percent acetylated cellulose groups. The diacetate fiber is officially called acetate while the triacetate cellulose is called triacetate.
Conventional secondary acetate fibers can be manufactured by treating wood pulp, cellulose or cotton linters with acetic acid. The pretreated cellulose or secondary acetate is converted to triacetate when treated with acetic anhydride in the presence of an acid catalyst.
Acetate fibers, the so-called acetate silk fibers, are molded from solutions of cellulose acetate in organic solvents, usually a mixture of methylene chloride and alcohol (triacetate), or acetone (secondary acetate).
Acetate fibers are soft and pleasant to the touch. They are dyed only with special types of dyes, which are unsuitable for most other fibers. Triacetate fibers are less hygroscope and have a greater elasticity and wrinkle resistance than articles made of diacetate fibers.
The tensile strength of acetate fibers is rather low. The loss of strength upon moist testing is up to 45 percent for acetate fibers and up to 20 percent for triacetate fibers.
Acetate fibers have a low thermal stability. For this reason, articles made of acetate fibers have to be ironed through a damp cloth. Furthermore, acetate fibers have a low stability in the presence of dilute solutions of alkalis. Other disadvantages of acetate fibers include low durability and high tendency to gather static electricity. To offset or remedy these deficiencies, acetates are often chemically modified or blended with other fibers.
Cellulose acetate fibers can be de-acetylated by sodium hydroxide saponification under controlled conditions. The product is a true regenerated cellulose filament. This process was developed by Celanese who called the fiber “Fortisan”. The fibers generic name is Rayon. It has outstanding strength and low elongation and finds many industrial uses where these two properties are required.
|Tensile Strength (Tenacity)||Fair to Poor|
|Heat Resistance||Fair to Poor|
|Wrinkle Resistance||Fair to Poor|
|Resistance to Sunlight||Fair to Poor|
|Elasticity||Poor (Similar to Rayon)|
|Flame Resistance||Slowly Combustible|
COMMERCIAL Cellulose acetate Fibers
Acetate fibers are mainly used in the production of general consumer articles including clothing, lining, felts, upholstery, carpets, umbrellas, and cigarette filters. The staple acetate fibers are also used as partial substitutes for wool in the manufacture of fine fabrics and various kinds of knitwear, for example, to reduce fiber / fabric shrinkage, to improve wrinkle resistance, and to lower raw material costs.